Rotary veneer sheet cutter

ABSTRACT

A rotary drum moves over an anvil in a veneer sheet handling apparatus. A knife is reciprocally mounted in the drum to protrude outwardly at selected intervals to sever the veneer. The peripheral tip speed of the knife is synchronized to correspond to the veneer sheet speed.

United States Patent Reppert 1 1 Apr. 8, 1975 1 1 ROTARY VENEER SHEET CUTTER 1.986.212 1/1935 Mahon 83/337 2.345072 3/1944 Rosenlea et a1. 83/337 X Repperh Blue Lake" 3.o57.239 10/1962 Teplitz 83/337 73 Assignee; Simpson Timber Company, Seattle 3.769.867 11/1973 Schll hng 83/338 X Wash. Primary E.raminer]. M. Me1ster Fled: 1974 Attorney, Agent, or Firm-Seed Berry, Vernon & 1211 Appl. Nu: 433,753 Buynham 52 us. (:1 1. 83/337; 83/285 [57] ABSTRACT [51] Int. Cl B271 5/08 A rotary drum moves over "cnecr shoe 5 pick] f Search 83/337 235 handling apparatus. A knife is reciprocally mounted in the drum to protrude outwardly at selected intervals 5 References Cited to sever the veneer. The peripheral tip speed of the UNITED STATES PATENTS knlfe 1s synchromzed to correspond to the veneer sheet speed. 1.7111408 4/1929 Murclund 83/337 1.965.523 7 1934 MacFurrcn 33/337 x 5 Claims. 10 Drawmg gur s PHENTEDAPR 819% SEiY-IY 1 [IF 5 JFIIGO FIG 11 MTENTED APR 8 i375 saw u o 5 FIG 8 6)" M VIXIII FIGOH 1 ROTARY VENEER SHEET CUTTER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to veneer sheet handling apparatus and. more particularly, to rotary cutters and breakers for separating sheets from a continuous strip of veneer.

2. Description of the Prior Art Strips of very thin wood veneer are cut from a block by a lathe and are fed in long lengths and at high speeds, for example up to a thousand feet per minute, to a tippling conveyor which distributes cut lengths of the veneer into trays. Heretofore, the strip was cut by air or mechanical breakers which impacted the strip, breaking it into sheets but leaving a ragged edge.

Sheet cutters have also been developed which use a moving blade that travels along with the sheet at a constant speed. Frequently the strip of veneer, however, is traveling at an unknonw variable speed ranging anywhere from startup at to l,000 feet per minute. With a constant speed knife the veneer is frequently broken due to large variation in speed at any particular time between the strip of veneer and the speed of the blade.

SUMMARY OF THE INVENTION It is an object of this invention to provide a veneer strip cutter which produces a smoothly cut edge.

It is another object of this invention to provide a ro tary knife veneer sheet cutter that has a blade tip speed synchronized with the speed of the veneer strip being cut.

It is another object of this invention to provide a timing device for a rotary knife veneer sheet cutter.

Basically, the objects of this invention are obtained by providing a rotating drum that is synchronized to travel at a speed just slightly less than the speed of the veneer strip. A knife is reciprocally mounted in the drum for selective radially outward movement to sever the veneer, the knife when extended traveling at a peripheral tip speed equal to that of the veneer strip speed. Means are provided for synchronizing the cutting sequence to cut the veneer cleanly at desired locations along the strip.

The synchronization between tip speed of the knife and the speed of the veneer strip and the sequencing at proper intervals to make the cut at the desired location along the strip are controlled by a unique timing device that includes a shaft having an eccentric cam, a knife rotatably mounted on the eccentric cam. clutch means for coupling the shaft with the drum so that the knife does not move relative to the cam. and brake means for stopping the shaft when the clutch is released to allow relative movement between the knife and the cam for protruding the knife outwardly from the drum, and means for re-aligning the shaft with the drum after each cutting cycle so that the shaft braking time to bring the shaft to a full stop is maintained accurately relative to the position of the knife for each cycle.

The rotary knife veneer cutter of the invention allows periodic accurately positioned cuts along a continuous strip of veneer without creating a ragged edge or breaking the veneer. The rotary drum assists in guiding the veneer past the knife actuation mechanism and particularly in controlling imperfect veneer having curled edges and the like. The timing mechanism provides an inexpensive and accurate technique for decelerating and recycling a heavy mass rotating at high peripheral velocities.

BRIEF DESCRIPTION OF THE DRAWINGS lt) junction with a veneer strip handling mechanism.

FIG. 4 is a section taken along the diameter of the rotary drum.

FIG. 5 is a fragmentary section taken along the line 5-5 of FIG. 4.

FIG. 6 is a fragmentary section taken along the line 66 of FIG. 7.

FIG. 7 is a fragmentary section taken along the line 7-7 of FIG. 6.

FIG. 8 is a fragmentary section of the brake and clutch employed in the cutter.

FIG. 9 is a schematic control diagram illustrating the timing principles of the invention.

FIG. I0 is an electrical schematic embodying the timing principles of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As best illustrated in FIGS. I and 2 the rotary knife veneer sheet cutter I0 is positioned over a conventional rotary anvil 12. The cutter and anvil are positioned at the discharge end of a high speed conveyor 14 that delivers a continuous strip of thin veneer from a lathe in a conventional manner. A conventional tipple conveyor 16 distributes cut sheets of veneer to various trays in a conventional manner. A motor powers a drive sprocket 18 which, through a belt roller chain 20, powers the conveyor drive 22, the tipple drive 24 and the rotary knife drive 26. It is an important feature of this invention that all of these drives be synchronized to travel at a constant speed ratio for proper timing of the cutting operation.

The cutter comprises an elongated drum 30 rotatably mounted on a stationary frame 32 (FIG. 8). The drum also is rotatably mounted by a bearing sleeve 34 (FIG. 7) to a shaft 36. The drum is connected to the sprocket of the drive 26 (FIG. 3) and is thus continuously driven. A conventional pneumatic clutch 38 selectively couples the sprocket and drum to the shaft 36 for conjoint rotation. A conventional pneumatic brake 40 (FIG. 2) decelerates the shaft at a controlled rate of speed to avoid shock and brings it to rest relative to the frame. Thus, in one operative mode, the shaft and drum rotate together whereas in the knife extension mode the drum continues to rotate but the shaft is stopped.

As best shown in FIG. 4 the shaft is provided with cam collars 42 which acuate cam rings 44. The cam collars carry a bearing sleeve 46 which is connected to cam rings 44. A plurality of knife bar holders 50 are secured to the cam rings 44 and at their outer end mount a continuous knife bar or cutting blade 52 of a length sufficient to extend transversely across the entire strip of veneer. Movement ofthe knife bar holders 50 within the drum 30 is controlled by guide rollers 54 spaced on either side of an elongated opening 56 (FIG. I) provided along the length of the drum. As is best shown in FIG. 4, when the shaft 36 and cam collars 44 are halted. the drum and knife bar holders 50 will continue to rotate on the cam collars. Since the cam collars are eccentric to the axis of the shaft 36. the knife bar 52 will move outwardly approximately four inches in the preferred embodiment, as shown in phantom in FIG. 4.

Since the friction brake which stops the shaft takes a finite amount of time to bring the shaft from its high speed of rotation to a full stop, it is necessary that timing of the actuation of the brake be directly correlated with the speed of rotation of the drum. This correlation will be obtained in a manner to be described below. It is also necessary, however, to assure exact alignment between the shaft and the drum at the start of each braking cycle to assure that the shaft comes to rest at the desired time. For this purpose the shaft and drum are repositioned exactly relative to each other after each cycle of cutting. As best shown in FIG. 6, the shaft is connected to a double acting air cylinder 60 having a piston rod 62 that is connected to a lever 64. The lever is rotatably connected to a roller or pawl 66. The shaft is secured to an alignment disc. 68 having a notch 70. The drum is secured to an alignment disc 72 having a notch 74. When the pawl 66 is seated in the two notches 70 and 74 the drum and shaft are at a predetermined aligned position with one another. Extension of the actuator piston rod 62 moves the pawl into the phantom line position shown in FIG. 6 to allow relative movement between the drum and the shaft. As will be explained in more detail below, at the end of each cutting cycle the pawl 66 is placed in both notches 74 and 70 locking them together in an alinged position.

The timing control for assuring accurate cutting of the veneer sheets is best shown in FIGS. 9 and 10. Supply air is brought in through a main line 80 at approximately 80 PSI and is reduced at a line 81 to approximately 40 PSI. Air then passes to a conventional electrical pneumatic speed transmitter 82 of a type manufactured by Moore Industrial Controls Company of Springhouse. Pennsylvania. The electrical pneumatic speed transmitter converts an electrical signal from an electrical tachometer 83 to a modulation of the air signal entering from line 81. In the preferred form the speed transmitter is capable of transmitting a variable air output signal to a line 84 in the range of O-IS PSI in direct proportion to the RPM of the machine which the electric tachometer 83 is sensing. In the preferred embodiment. the electric tachometer 83 is sensing lathe operational speed which determine the speed at which the veneer strip is moving.

Control air coming through the line 84 is then bal anced against the 40 PSI air in line 8] and controls a double acting air cylinder 86. The piston rod of the cylinder 86 is connected to a swivel timing plate 88. The position ofthe timing plate circumferentially about the axis of shaft 36 is thus dependent upon the RPM of the machine sensed by the tachometer 83. The position of the pawl 66 is controlled by a valve 90 that is a fourway two-position solenoid actuated valve. The clutch 38 is controlled by a two-position three-way solenoid actuated valve 92. The air brake is controlled by a twoposition three-way solenoid operated valve 94. Operational sequence for these valves is best shown in the electrical schematic of FIG. 10.

Switch RH-2 is closed automatically either from the lathe sheet measurement control in a conventional manner which signals when a sheet is to be cut or from a limit switch on the veneer sheet trays or any other conventional manner. This control signal passes along a circuit through a manual selector switch SL.S-l which when closed then allows the signal to energize the latch relay LRI. Energization of latch relay LRl closes switch contacts LR-la. As best shown in the lower righthand drawing of FIG. 7 the drum 30 is provided with a metallic target or switch actuator 96 that is rotated past two circumferentially spaced proximity switches PS1 and PS-Z located on the oscillatable timing plate 88. As the target 96 passes biased open switch contact PS-l, switch contacts PS-la are momentarily closed, energizing relay CR-l-l, Relay contact CR-la becomes closed, energizing rachet relay RR-l. Rachet relay contacts RRla are closed, energizing latch relay LR-Z. Latch relay contacts LR2a become closed, energizing the brake solenoid of valve 94. The latching relays LR-] and LR-2 have companion sets of contacts requiring a signal to latch the contacts or close them and a separate signal to the other side of the coil ULR1 and ULR-Z to unlatch or open the contacts. Thus, once contacts LR-2, for example. are closed they remain closed until opened by energization of unlatch relay ULR-Z. Continuing with the circuit relay contacts LR-Zb release the clutch. and LR2c energize the sychronizing pawl actuator 90, pushing pawl 66 out of the notches 74 and 70. As a result ofthe energization of the brake and the de-energization of the clutch. the shaft begins to come to rest and the drum continues to rotate at a speed corresponding to the speed of the veneer sheet. At the same time, contacts LR-Zd energize unlatch relay ULR-l to re-open contacts LR-la to de-energize the circuit connected to proximity switch contacts PS-Ia.

The knife bar has now rotated along with the drum relative to the shaft and has slid along the cam outwardly of the drum to sever the sheet of veneer from the strip. Since the drum rotates at a variable speed directly relating to the speed of the veneer it is, of course, necessary that the energization of the brake, clutch and paw] circuits be varied to assure that the brake stops the shaft at the desired moment. This control is obtained through the speed transmitter 82 which controls the double acting air cylinder 86 and the timing plate 88 which mounts the two proximity switches PS] and PS2. In other words, as viewed in FIG. 10 a shift counter clockwise of the timing plate 88 relative to the axis of the drum 30 will cause an advance in energization of the brake. clutch and pawl actuating circuits. After the cut is obtained, the target then passes proximity switch PS2, closing proximity switch contact PS-Zu. energizing a time delay relay TDR. Contacts TDR-Z are opened simultaneously with closing contacts TDRI and double acting cylinder 60 pulls the synchronizing pawl toward the notch 70, but the pawl cannot move into the notch because it is held out by the plate 72 since the notches 74 and 70 are not aligned. The brake solenoid is then de-energized or jogged as the target 96 again passes proximity switch PSI for the second time. Contacts PSI(' and PS-lb are closed. Closing contacts PS-lc energizes relay CR-l-2. Energizing relay CR-l-Z closes contact CR2a. This energizes relay RR-2 closing contacts RR-2u. Closing contacts RR-Za energizes unlatch relay ULR2, opening all ofthe contacts LR2a-d. The contacts of switch PS-I and PS-Z automatically open after being closed by actuator 96. Contacts RR-Zu are therefore reopened as relay RR-Z becomes deenergized as are contacts CR-lu opened by deenergization of relay CRl-l.

As the pawl 66 which remains out or in the phantom position in FIG. 7 is carried past switch LS2, it contacts the switch closing contact LS-Za. Contact LS-Za is a spring-biased open switch which instantaneously energizes the brake solenoid 96 to momentarily slow the shaft 36 and thus the plate 68. This allows the plate 72 with its notch 74 to advance on the notch 70 until the two notches come aligned and the pawl 66 automatically is drawn into place, locking the two plates together and thus locking the shaft again to the drum. As the pawl 66 previously had passed latch contacts LS-l, it closes the spring-biased contact LS-la momentarily to light a signal RR-Z to indicate that the pawl is still in the proper cycle and not out of phase by 180. A signal is also sent from the circuit (dotted lines) in which contacts LS-la are located to the main lathe control to indicate that a cycle has been completed, a sheet has been cut and conditions it for receiving the next signal to cut the next sheet.

As thus can be seen, the electrical pneumatic control provides synchronism of brake actuating signals with speed of the drum which is related to speed of the sheet. This assures that the knife bar is always engaged with the sheet at proper time and in synchronism with the speed of the sheetv Proximity switch PS-2 is generally manually positioned; that is, set by trial and error, and once set remains properly positioned for the particular machine.

While the preferred embodiment of the invention has been illustrated and described, it should be understood that variations will be apparent to one skilled in the art. Accordingly, the invention is not to be limited to the specific form illustrated.

I claim:

I. A veneer cutter comprising:

infeed conveying means conveying a continuous sheet of thin wood veneer along a path,

a rotary veneer sheet cutter in the path. the cutter including t l) a rotary drum, (2) a single knife bar carried within the drum, and 3) means for moving the knife bar between a retracted position within the drum and an extended position outwardly of the drum and into the path of the traveling veneer to cut the veneer,

drive means driving the infeed conveying means and rotary veneer sheet cutter at a constant speed ratio to give the tip of the knife bar in extended position a peripheral speed approximately equal to the speed of the veneer, and

coupling means for selectively coupling the means for moving the knife bar and the rotary drum together for conjoint rotation with the rotary drum causing retraction of the knife bar to the retracted position and for braking the means moving the knife bar relative to the drum to cause extension of the knife bar to the extended position to cut the veneer.

2. The cutter of claim 1 wherein the means for moving the knife bar includes a rotatable shaft coincident with the axis of the rotary drum, a cam eccentrically mounted on the shaft, the knife bar mounted to travel over the eccentric cam, and wherein the coupling means includes clutch means coupling the rotary drum and shaft together for moving the cam with the rotary drum and holding the knife bar in the retracted position within the drum during rotation, and brake means operable to stop rotation ofthe cam means relative to the rotary drum, causing the knife bar to rotate about the eccentric cam and extend outwardly of the rotary drum to the extended position, and

aligning means for repositioning the shaft relative to the rotary drum on retraction of the knife bar for controlling movement of the knife bar outwardly,

3, The cutter of claim 1 wherein the aligning means includes( l a pair of notched plates, one connected to the rotary drum and the other to the shaft, (2) a pawl for registering in the notches to align the drum and shaft, and (3) means for temporarily adjusting the relative speed between the shaft and the drum to allow the two plates to move at different speeds until the notches are aligned.

4. The veneer cutter of claim 1 wherein the brake means is a pneumatic brake for decelerating the shaft at a controlled rate,

5. The veneer cutter of claim 1 wherein the clutch means is a pneumatic clutch for coupling the shaft and brake means together when the brake is deenergized. =l 

1. A veneer cutter comprising: infeed conveying means conveying a continuous sheet of thin wood veneer along a path, a rotary veneer sheet cutter in the path, the cutter including (1) a rotary drum, (2) a single knife bar carried within the drum, and (3) means for moving the knife bar between a retracted position within the drum and an extended position outwardly of the drum and into the path of the traveling veneer to cut the veneer, drive means driving the infeed conveying means and rotary veneer sheet cutter at a constant speed ratio to give the tip of the knife bar in extended position a peripheral speed approximately equal to the speed of the veneer, and coupling means for selectively coupling the means for moving the knife bar and the rotary drum together for conjoint rotation with the rotary drum causing retraction of the knife bar to the retracted position and for braking the means moving the knife bar relative to the drum to cause extension of the knife bar to the extended position to cut the veneer.
 2. The cutter of claim 1 wherein the means for moving the knife bar includes a rotatable shaft coincident with the axis of the rotary drum, a cam eccentrically mounted on the shaft, the knife bar mounted to travel over the eccentric cam, and wherein the coupling means includes clutch means coupling the rotary drum and shaft together for moving the cam with the rotary drum and holding the knife bar in the retracted position within the drum during rotation, and brake means operable to stop rotation of the cam means relative to the rotary drum, causing the knife bar to rotate about the eccentric cam and extend outwardly of the rotary drum to the extended position, and aligning means for repositioning the shaft relative to the rotary drum on retraction of the knife bar for controlling movement of the knife bar outwardly.
 3. The cutter of claim 1 wherein the aligning means includes (1) a pair of notched plates, one connected to the rotary drum and the other to the shaft, (2) a pawl for registering in the notches to align the drum and shaft, and (3) means for temporarily adjusting the relative speed between the shaft and the drum to allow the two plates to move at different speeds until the notches are aligned.
 4. The veneer cutter of claim 1 wherein the brake means is a pneumatic brake for decelerating the shaft at a controlled rate.
 5. The veneer cutter of claim 1 wherein the clutch means is a pneumatic clutch for coupling the shaft and brake means together when the brake is deenergized. 